Method for making reflex copies



ug 18, 1936- P, F. VAN DER GRINTEN 2,051,583

METHOD FOR MAKING REFLEX COPIES I Filed Dec. 1v, 19:54

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Patented Aug. 18, 1936 PATENT OFFICE 2,051,583 y METHOD Fon MAKINGREFLEX norms Lodewijk Pieter Frans van der Grinten, Venlo,

Netherlands, assignor to Naamlooze Vennootschap Chemische Fabriek L. vander Grinten, Venlo, Netherlands, a limited-liability company ofNetherlands Application December 17, 1934, Serial No. 757,933 In theNetherlands December 19, 1933 12 Claims.

, It is known to make reex copies by a method comprising the steps ofapplying on an original a sheet containing a layer of bromicjsilveremulsion subjecting the original to a radiation through said sheet andsubdividing said radiation before it passes through the layer ofsensitive material into small areas of lower and higher photochemicalpower. This method, however, does not give good reflex copies.

Now it has been found that good reflex copies can be obtained by othermethods to be further described, whilst the type of the rays employedmay be also of importance.

If one compares with the help of the microscope those parts of thereflex copy that were'during u the production of the latter over thedark regions smaller photochemical action has occurred. The

result of this action is hereinafter called the ha1o; vit may forexample be practically expressed by the reduction of the covering factorof the screening of the portions in question (the covering factor beingthe surface of the regions of smaller photochemical action, or the correspending regions in 'the reflex copy, per unit of surface).

Now it has been-found that the halo exerts a.

large injurious influence on the strength of the picture; The object ofthe present invention is therefore to limit this halo. Whereverhereinafter reference is made to rays, or to transparency or to capacityof reflexion therefore, this always means that reference is made to raysof A such wave lengths as influence photochemically the sensitive layeror layers employed.

The requirements necessary for the practical avoidance of a halo in thesensitive sheet are dependent on many different factors, vlikewise theimportance of the halo.itself.- They are determined inter alia by thekind and the coarseness of the subdivision into regions of greater andof the nature of the sensitive Alayers employed and the diffusion of therays by these layers.

In order to diminish the halo it is requiredto avoid a diffusedradiation into the areas of smaller actinic intensity. It has been foundthat one necessary condition to obtain this is the use of a sensitivelayer, which-at least during a considerable part of the necessaryirradiation-has a high coeiiicient of directed propagation for the raysby which the image is formed.

The expression coefficient of directed propagation of a sensitive laye/1for definite rays is defined as the. reversed ratio between the actinicintensity of a small band (the smallest dimension of which should notexceed the thickness of the layer) of parallel rays of the kind employedas it is measured when perpendicularly impinging upon the front surfaceof the sensitive layer and. the actinic intensity of this band of raysafter passing through the sensitive layer asit is measured in the areawhich is the perpendicular projection of the area of the front surfaceupon whichsaid band impinges on the back surface of -said layer.

There are several sensitive layers capable of further be taken intoaccount for example the quantity of sensitive material present and itsdistribution in the sensitivel sheet. For this reason, for the purposeof reducing lthe halo it is advantageous to have the quantity of thesensitive material as small as possible, which will in many casespresent at the same time the advantage that smaller quantities of theradiation suiice for the production of the reflex copy. The

picture production is of course determined simply by the reflectedradiation and this radiation is only small owing to the restrictedcapacityfor reflexion of the originals that occur in'- practice and, i'nthe case of covering screening, of the restricted amount of theradiation energy passing into' the system, s'o that for these reasonsalready the operation is uneconomical as regards the 'useful effect ofthe radiatibn. -Of -course, with a layer containing less` sensitivematerial, for instance a thin layer, there is obtained also a smallerpicture strength, which, however, may be increased by recopying. Wherehereinafter it is a question of strong reflex copies there are meantthereby copies that are strong in relation to the layer employed in themaking of them.

In all these cases an improvement is obtained by using a sensitivelayer, which-at least during a considerable part of the necessaryirradiation by said rays-has not only a high coefficient of directedpropagation but in which also the ratio 'between the amount of radiationdiffused into the sensitive layer and the radiation leaving thesensitive layer in the direction of the original is small. y f

If dispersion should not be avoided completely it should be caused totake place during the production of the reflex copy merely in the spacelocated between the sensitive layer or the sensitive layers, and theoriginal.

A special selection of the rays to be employed is of course ofimportance merely for layers that are sensitive over a comparativelywide range of wave lengths. Within such a range the transparency and theray dispersion may vary with the wave length. In such a case there arepreferably chosen, in as far as theselectively reflecting properties ofthe original allow of this in the sense of what has been said, thosewave lengths for which the transparency is the greatest and the raydispersion is the smallest. As an example for this there may bementioned the employment of a yellow lter.

It may be here mentioned that in the case of comparative tests fordetermining an effect according to the invention all the factors thatcan affect the magnitude and the importance of the halo, other than thenature of the sensitive layers, as, inter alia, the above mentionedfactors, must remain constant and only the nature of the sensitive.layer with respect to the rays employed should vary.

It is also to be assumed and taken for granted that the sensitive layerswork contrasting to a reasonable extent.

It has further been found that it is not necessary that a highcoefficient of directedpropagation exists in the sensitive layer alreadyin the beginning of the process for making the reflex copy. There aresensitive materials wh'ch are decomposed by the radiation into substancs having a much increased transparency for such rays. In that case thecoefiicient of directed propagation increases by the initial irradiationto a maximum when all the sensitive material in the regions of greateractinic intensity has been decomposed. Such layers generally absorb theradiation until they are completely decomposed but do not diffuse theradiation or only to a Very small extent. This makes these layers verysuitable for the purpose of the present invention. Examples of suchlayers are cyanotype layers, layers containing a sensitive iron saltwhich can be developed by means of galli'c acid and chromate layers thatbleach to a colourless substance.

The following examples serve to illustrate the invention which is by noway limited thereto. The examples will be described in connection withthe accompanying diagrammatic drawing which shows in crosssection acovering screen, a sensitive sheet and partof an original.

Example 1 An original O (see figure) which consists of a sheet ofclear-white paper printed on both sides with black printing, is placedwith the side upward from which it is desired to make a reflex copy. Onthis there is placed with upwardly turned emulsion layer, a celluloidsheet (DR) 0.1 mm. thick, which is provided with a normal silver halidegelatine layer (GL), 0.01 mm. thick,

` and thereon a lined covering screen (R) (made Irradiation is effectedthrough a yellow lter by means of an electric incandescent lamp of wattsat a distance of 40 cm. in the middle in front of the system so that therays impinge rst upon the screen, then upon the sensitive layer, andfinally upon the original.

After adequate irradiation, development takes place and xing is effectedin an ordinary manner. There is obtained a negative reflex copy in thetransparent portions of which (these are consequently the portions thatin the making of the reflex copy were laid over the black part of theoriginal Z, indicated in the drawing by hatching in O) the coarseness(by which is meant here the width of the transparent lines thatcorrespond in each case to the covering lines of the screen) is reducedfrom 0.14 to 0.10, and the covering factor (here consequently the ratioof the transparent surface to the total surface, measured between thelimits of the transparent portions) is consequently reduced from 0.82 to0.59, so that there has occurred a halo of 0.23.

If, instead of working according to the method in which the abovementioned emulsion is employed, there is employed a grainless so-calledLippmann emulsion, which is clear, the halo is too' small to bemeasured. The coarseness in the transparent portions is then exactly0.14. In the case of the employment of this emulsilon there'v may bealso employed white light (sun ight, incandescent lamp without yellowfilter). There is then obtained in the pervious portions o f thenegative reex copy a coarseness of 0.13, corresponding to a coveringfactor of 0.76 and conse- 'quently a halo of 0.82-0.76=0.06.

-In the case of the employment of normal Kodak film there would beobtained for example a coarseness of 0.09, i. e. a halo of 0.29, whichis so great that the reflex copy is hardly better than the onelobtainable with the same film in the old way without any screen.

Of course all the measurements were made under exactly like `conditionsso that the results were comparable.

Example 2 An original, a sensitive sheet, and a screen for example bysapniflcation. The sensitive solution employed consists of 10 parts byweight of green ferric ammonium citrate 1 part by weight of potassiumferriccyanide,

and 20 parts by volume of water.

The rear side of this sheet is matted that is to say rendered dull forthe purpose of increasing the legibility of the reflex copy to be made.

This layer has when unirradiated little transparency to the chemicallyactive rays; during the irradiation this transparency continuouslyincreases and has become comparatively great when the irradiation isfinished, and the layer has obtained a. high coeiicient for directedpropagation.-

An arc lamp at a distance of 40 cm. serves as the source of radiation.

After completion of the irradiation the sensitive sheet is measuredmicroscopically. The colourless portions have a coarseness of ,0.12 andconsequently a halo of 0.12. Washing is now eiected in a dilutepotassium ferric cyanide solution and then in water.

A strong negative rei-lex copy is obtained.

If the rear side of the sheet is not matted there is a coarseness of0.l4and consequently no halo.

Example 3 The operation is exactly like in Example 2 (see the drawing).The'sensitive sheet consists vof a Celluloid sheet 0.10 mm. thick, whichis provided with a gelatine sensitive iron salt layer 0.01 mm. thick,which was prepared with a solution of Percent Ferric sulphate Ferricchloride 3 Tartaric acid 5 Percent Gallic acid 0.7 Oxalic acid 0.1

and then immersion in a strong formaline bath.

There is obtained a strong positive reflex copy. When there is employeda lens covering screen the irradiation times are reduced.

Eample 4 For thepurpose of enabling comparison to be made, the operationagain takes' place in the manner stated in the foregoing examples (seethe drawing).

A sensitive bleaching chromate layer is produced by impregnating on itssaponied side a unilaterally saponiiied acetylcellulose sheet with asolution of Parts by weight Bichromate of potassium 1 Phosphoric acid,sp. gr. 1.32 3 Water 2 This layer is yellow coloured and.becomes onirradiation practically colourless. Consequently its transparency torays at the conclusion of the irradiation is great inthe regions ofgreater photochemical activity, after .the completion ofcontaining asensitive layer of the type which exhibits a high coeiiicient ofdirected propagation for the rays by which the image is formed for atleast a considerable part of the required irradiation, said layer beingselected from the group consisting of Lippman emulsion layer, cyanotypelayer, sensitive iron salt layer, bleaching chromate layer, subjectingtheoriginal to a radiation through said sheet, and subdividing saidradiation before it has passed through said layer into small areas oflower and higher photochemical power.

2. A process for making reex copies comprising the-steps lof applying onan original a sheet containing a sensitive layer of the type whichexhibits a high coefficient of directed propagation for the rays bywhich the image is formed forat least a considerable part of therequired irradiation, said layer being a Lippmann emulsion layer,subjecting the original to a radiation through said sheet, andsubdividing said radiation before it has passed'through said layer intosmall areas of lower and higher photochemical power.

3. A process for making rei-lex copies comprising the -steps of applyingon an original a sheet containing a sensitive layer of the type whichexhibits a high lcoeicient-of directed propagation for the rays by whichthe image is formed for atleast a considerable part of the requiredirradiation, said layer being a `cyanotype layer,

subjecting the original to a radiation through said sheet, andsubdivlding said radiation before4 it haspassed through said layer intosmall areas of lower and higher photochemical power.

4. A process for making reflex copies` comprising the steps of applyingon'an original a sheet containing a sensitive layer of the type whichexhibits a high coeilicient` of directed propagation for the rays bywhich the image is formed for at least a considerable part of therequired irradiation, said layer being a bleaching chromate layer,subjecting the original to a radiation through said sheet, andsubdividing said radiation before it has -passed through said layer intosmall areas of lower and higher photochemical power.

5. A process for making reflex copies comprising the steps of A,applyingon an original a sheetl containing a sensitive layer of the type whichexhibits a high coefficient of directed propagation for the raysby whichthe image is formed for at least a considerable part of the requiredirradiation, said layer being selected from the group consisting ofLippmann emulsion layer, cyanotype layer, sensitive iron `salt layer,bleaching chromate layer, subjecting the original to a radiation throughsaid sheet, and subdividing said radiation by the application of ascreen before it passes through said layer'into small areas of lower andhigher photochemical power.

6. A process for making reflex copies compris- 4ing the steps ofapplying on an original a sheet containing a sensitive layer of the typewhich exhibits a high coefcient of directed propagation for the rays bywhich the image ls formed for at least a considerable part of therequired irradiation, said layer being a Lippmann emulsion layer,subjecting the original to a radiation through said sheet, andsubdividing said radiation by the application of a screen before itpasses through said layer into small areas of lower and higherphotochemical power.

7. A process for making reflex copies comprising the steps of applyingon an original a. sheet containing a sensitive layer of the type whichexhibits a high coefficient of directed propagation for the rays bywhich the image is formed for at least a considerable part of therequired irradiation, said layer being a cyanotype layer, subjecting theoriginal to a radiation through said sheet, and subdividing saidradiation by the application of a screen before it passes through saidlayer into small areas of lower and higher photochemical power.

8. A process for making reex copies comprising the steps of applying onan original a sheet containing a sensitive layer yoi the type whichexhibits a high coeiiicient of directed propagation for the rays bywhich the image is formed for at least a considerable part of therequired irradiation, said layer being -a bleaching chromate layer,subjecting the original to .a radiation through said sheet, andsubdividing said radiation by the application of a screen before itpasses through said layer into small areas of lower and higherphotochemical power.

9. A process for making reflex copies comprising the steps of applyinglon an original a sheet Acontaining a sensitive layer of the type whichexhibits a high coefficient of directed propagation for the rays bywhich the image is formed for at least a considerable part of therequired irradiation, said layer being selected from the groupconsisting of Lippmann emulsion layer, cyanotype layer, sensitive ironsalt layer, bleaching chromate layer, subjecting the original to aradiation through said sheet, and subdividing said radiation before ithas passed through said layer into small areas of lower and higherphotochemical power, said sheet being diffusing only in the spacebetween the sensitive layer and the original.

10. A process for making reflex copies comprising the steps of applyingvon an origin-al a sheet containing a sensitive layer of the type whichexhibits a high coeicient of directed propagation for the rays by whichthe image is formed for at least a considerable part fof the requiredirradiation, said layer being a Lippm-ann emulsionlayer, subjecting theoriginal to a radiation through said sheet, and subdividing saidradiation before it has passed through said layer into small areas oflower and higher` photochemical power, sai-d sheet being diffusingonlyvin the space between .the sensitive layer and the original.

11. A process for making reflex copies comprising the steps of applyingon an origin-a1 a sheetcontaining asensitive layer of the type whichexhibits a high coeiiicient of directed propagation for the rays bywhich the image is formed for at least a considerable part of therequired irradiation, said layer being a cyanotype layer, subjecting theoriginal to a radiation through said sheet, and subdividing saidradiation before it has passedthrough said layer into small areas oflower and higher photochemical power, said sheet being dilusing only in'the space between the sensitive layer and theI original.

12. A process for making reilex copies comn radiation before it haspassed through said layer intoI small areas of lower and higherphotochemical power, said sheet being diffusing only in the spacebetween the sensitive layer and the originali LODEWIJ K PIETER FRANS VANDER GRINTEN.

